Filter devices used for purifying or separating fluids such as liquids or gases may be classified into a disposable type in which the filter element encased therein is not exchangeable and an exchangeable type in which the filter element encased therein is exchangeable. The disposable type filter device is uneconomical and resource-wasting because a large volume of synthetic resin is used for forming a housing for encasing the filter element and a lid (fixed head) provided with fluid inlet and outlet.
On the other hand, the exchangeable type filter comprises, as described in JP10-110657 A, JP 8-200572 A and JP 5-361212 A, a fixed head having a manifold provided with an inlet and an outlet, and a housing containing therein a filter element. The housing is detachably connected at one end with the fixed head so that the filter element can be exchanged. Such exchangeable type filter device may be classified into the following types.
(1) At a mating portion between the fixed head and the housing, a male thread is formed on an outer rim of the fixed head, an outer rim of the housing is supported by an idle ring having a female thread on its inner periphery, and the female thread of the idle ring is threaded onto the male thread of the fixed head to connect the housing to the fixed head.
However, it is troublesome to carry out the screwing operation while holding the weight of the housing against the gravity, especially when the housing has a large weight, and all the more troublesome when the housing is made of stainless steel.
(2) At the mating portion between the fixed head and the housing, rims projecting outward are respectively formed on the fixed housing and the housing and these rims are tightened together with a clamp band or ring band.
(3) At the mating portion between the fixed head and the housing, rims projecting outward are respectively formed on the fixed housing and the housing, a plurality of through-holes are formed in the rims at given intervals and these rims are tightened together with bolts and nuts utilizing the through holes.
In the cases (2) and (3), too, operations of supporting the weight and tightening the clamp or bolts is laborious if the size of the housing is large, especially when a stainless steel housing is required.
Patent Literature 1: JP 10-110657 A
Patent Literature 2: JP 8-200572 A
Patent Literature 3: JP 5-361212 A
With the case (1) above, it is difficult to turn the threaded ring many times about the threaded fixed head while holding with a hand the housing containing a filter element against the gravity, especially when the housing has a large weight.
In the case (2) above, in order to assemble or exchange the filter device, the housing containing a filter element is first held by a hand or hands against the fixed head to engage the rims to each other, the clamping band is fit over the rims, and then the band is tightened by pulling it with a clamping fixture (bolt and nut, for example) mounted on both ends of the clamping band. This operation is difficult for one operator because it is required to align the housing as well as the clamping band to a predetermined position of the fixed head, a large force is necessary especially when the weight of the housing and the filter element is heavy, the housing falls down during the tightening operation if the alignment is not properly done, and tightening and removal of the clamping band are laborious and time-consuming operations.
In the case (3), too, it is necessary to hold the housing against the fixed head by a hand or hands to put the peripheral rims together, in such manner that the through-holes are registered, and the rims are tightened together with bolts and nuts using the trough-holes.
On the other hand, disengagement of the housing requires similar complicated and time-consuming jobs.
Accordingly, an object of the present invention is to provide a filter device of the type that the housing is reusable and the filter element is exchangeable, which is free of the above-described drawbacks and the connection and disconnection of the housing for replacement of the filter element can be easily performed by simple operations.